Metabolic Rate (BMR / TDEE)
Estimate your basal metabolic rate (BMR) using the validated Mifflin-St Jeor 1990 equation, then convert it to total daily energy expenditure (TDEE) with an evidence-based activity multiplier. You'll also get calorie targets for fat loss, maintenance, and lean-mass gain.
Patient Parameters
Mifflin-St Jeor uses biological sex for the BMR offset.
Use your most recent reliable measurement.
Formulas used
Men: 10 × kg + 6.25 × cm − 5 × age + 5 Women: 10 × kg + 6.25 × cm − 5 × age − 161 TDEE = BMR × Activity Multiplier Aggressive cut: TDEE − 750 Fat loss: TDEE − 500 Maintenance: TDEE Lean-mass gain: TDEE + 250 Enter your sex, age, height, weight, and activity level — then tap Calculate.
Calorie targets by goal
Result Interpretation
Want to know what's actually driving your metabolic rate?
BMR estimates from a formula are useful, but real metabolic rate depends on thyroid output, body composition, mitochondrial efficiency, and hormone status, variables that the Mifflin-St Jeor equation can't see. A full evaluation measures these directly so we can plan around your physiology, not a population average.
Evidence & Sources
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. Am J Clin Nutr. 1990;51(2):241-247. A new predictive equation for resting energy expenditure in healthy individuals.
- Frankenfield D, Roth-Yousey L, Compher C. J Am Diet Assoc. 2005;105(5):775-789. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review.
- Roza AM, Shizgal HM. Am J Clin Nutr. 1984;40(1):168-182. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass.
- Hall KD. Int J Obes. 2008;32(3):573-576. What is the required energy deficit per unit weight loss?
- Slater GJ, Dieter BP, Marsh DJ, Helms ER, Shaw G, Iraki J. Front Nutr. 2019;6:131. Is an energy surplus required to maximize skeletal muscle hypertrophy associated with resistance training?
- Iraki J, Fitschen P, Espinar S, Helms E. Sports. 2019;7(7):154. Nutrition recommendations for bodybuilders in the off-season: a narrative review.
- Helms ER, Aragon AA, Fitschen PJ. J Int Soc Sports Nutr. 2014;11:20. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation.
Clinical Disclaimer: This calculator applies the Mifflin-St Jeor equation and standard activity multipliers to estimate basal and total daily energy expenditure. Predictive equations have a typical accuracy of ±10% in healthy adults and lose accuracy in athletes, individuals with very high or very low body fat, the elderly, and those with thyroid or other endocrine disorders. The calorie targets shown are reasonable starting points, not prescriptions, actual intake should be adjusted based on observed body-weight and body-composition trends over 2–4 weeks. This tool is for educational and decision-support use only and does not substitute for individualized clinical judgment.
About BMR & TDEE
What's the difference between BMR and TDEE?
BMR (basal metabolic rate) is the energy your body burns at complete rest, just keeping your organs running. TDEE (total daily energy expenditure) is BMR plus everything else: digestion, daily movement, exercise, and non-exercise activity thermogenesis (NEAT). TDEE is the number that actually matters for weight management.
Why use Mifflin-St Jeor instead of Harris-Benedict?
Mifflin-St Jeor was developed in 1990 specifically to address the inaccuracies in the original Harris-Benedict equation, which was derived from a small sample in 1919. Multiple systematic reviews (including Frankenfield 2005) have shown Mifflin-St Jeor is the most accurate predictive equation for healthy adults across a wide BMI range.
How accurate is this calculator?
For healthy non-athletic adults, Mifflin-St Jeor predicts BMR within roughly ±10% of measured values from indirect calorimetry. Accuracy drops in highly muscular athletes (BMR underestimated), individuals with very high body fat (overestimated), and people with thyroid or other endocrine conditions. Treat the number as a starting point, not a prescription.
How fast should I lose weight?
A 500 kcal/day deficit produces about 1 lb (0.45 kg) of fat loss per week, which is the rate most evidence-based guidelines recommend for sustainable fat loss with lean-mass preservation. Faster loss is possible but increases the risk of muscle loss, metabolic adaptation, and rebound. Pair any deficit with resistance training and at least 1.6 g/kg/day of protein.
What if my weight isn't changing as predicted?
After 2–3 weeks of consistent intake, if your weight trend isn't matching the goal, adjust intake by 100–200 kcal/day in the appropriate direction. Real-world TDEE varies day to day with NEAT, sleep, hydration, and stress. The calculator is the starting point; your scale and tape measure are the feedback loop.
Can low calories actually slow my metabolism?
Prolonged aggressive deficits (>25% below TDEE for >12 weeks) can cause adaptive thermogenesis, where measured BMR drops 5–15% below predicted. This is one reason we recommend the moderate −500 kcal target for most people, and periodic diet breaks at maintenance for longer cuts.